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Earth gets a new companion for trip around sun

ADD one to the entourage. Newly discovered asteroid 2014 OL339 is the latest quasi-satellite of Earth.

The asteroid, which is between 90 and 200 metres in diameter, has been hanging out near Earth for about 775 years. It will move on in about 165 years, say Carlos and Raul de la Fuente Marcos at the Complutense University of Madrid in Spain, who have just described it (arxiv.org/abs/1409.5588v1).

Quasi-satellites orbit the sun but are close enough to Earth to look like companions. Earth’s gravity has guided 2014 OL339 into an eccentric wobble, which causes the rock to appear to circle backwards around the planet.

With four quasi-satellites catalogued so far, Earth comes in second to Jupiter’s six, though the gas giant probably has many more that we can’t see. The same is likely true of Earth, as small space rocks are notoriously hard to find.

This article appeared in print under the headline “Earth gets a new companion”